16s DNA sequence of extraction blank from 220524 extraction samples
DNA was extracted using Zymo Quick-DNA Fecal/Soil Microbe Microprep Kit according to instructions. Aliquots of extracted DNA were sent to WrightLabs (Huntingdon, Pennsylvania, USA) for library preparation and sequencing.  DNA concentrations were quantified using an Invitrogen Qubit 4 Fluorometer and 1X Qubit dsDNA High Sensitivity Assay Kit (ThermoFisher Scientific, Waltham, MA, USA). All 16S rRNA illumina-tag PCR reactions were performed on DNA extracts per the Earth Microbiome Projects protocol (Walters et al. 2016). A negative control (PCR grade nuclease-free water) was processed in parallel with the samples for PCR amplification. PCR products were pooled and gel purified on a 2% agarose gel using the Qiagen Gel Extraction Kit (Qiagen, Germantown, Maryland, USA). No negative controls had amplification and were therefore not added to the sample pool. Before sequencing, the purified pool was quality checked using an Agilent 2100 BioAnalyzer and Agilent DNA High Sensitivity DNA kit (Agilent Technologies, Santa Clara, California, USA). The purified pool was stored at -20C and then sequenced using an Illumina MiSeq v2 chemistry with paired-end 250 base pair reads.